A minute amount of glue (also called as “gelatin”) is frequently added into an electrolyte solution used in a method for production of an electrolytic copper by electrolytic smelting, a method for production of a foil of electrolytic copper, and the like. Glue is added for effecting a role of controlling an appearance, mechanical strength, surface crystal structure, physical properties such as roughness of the electrolytic copper and foil of electrolytic copper. It is important for producing a product having a stable quality to control the concentration of glue in the electrolyte solution. Particularly, in the field of the electrolytic smelting of copper, while a method called as a permanent cathode method (PC method) is becoming a major method in which a stainless steel plate is used as a cathode plate onto surface of which copper is electrolytically deposited, it is required to strictly control the concentration of glue when electrolytic copper is produced using the PC method, and therefore, management of the concentration of glue may become more important.
However, the concentration of glue in an electrolyte solution is low, which is in the order of ppm (or mg/L), and therefore its quantitative analysis has been difficult. Further, glue is liable to be degraded by sulfuric acid of high concentration included in the electrolyte solution into low molecular weight substances. Thus, when a long time is required for the analysis, the degradation of glue proceeds during the analysis and an analytical result does not accurately reflect the actual concentration of glue included in the electrolyte solution.
Thus, various types of technologies for analyzing the concentration of glue contained in the electrolyte solution in a minute amount have been proposed. For example, Japanese Patent Application Unexamined Publication No. 2001-337081 discloses an analytical means using high performance liquid chromatography. Concretely, it discloses a method for determining the concentration of glue or gelatin or a distribution of molecular weight thereof comprising the steps of separating glue in an electrolyte solution and an electrolyte component by using a column charged with a filler in the size exclusion mode as a column for high performance liquid chromatography for separating, introducing the glue-containing fluid from which said electrolyte component have been separated into another column charged with a filler in the size exclusion mode, separating the glue according to the molecular weights or distribution of molecular weights, and then introducing the fluid containing the separated glue into a detector.
According to the method described in this document, not only the concentration but also the molecular weight can be analyzed. Therefore, it is a useful method for analyzing a minute amount of glue contained in an electrolyte solution. However, in order to perform an analysis of concentration of glue according to the method, connecting two separation columns in tandem, equipping both of the former and latter columns with a detector, and changing the flow of the fluid timely with a six-way changing valve and the like are required, which makes the analysis system complex. Further, since it is necessary for glue to pass through the two columns, there is a concern that the degradation of glue may occur during the passing.
Further, while this document describes the use of a mixture of sulfuric acid and acetonitrile as a mobile phase, acetonitrile necessitates the trouble for treating waste organic solution.